Public Relations Chief of the State Railway of Thailand (SRT), Nuan-anong Wongjan, told reporters that the accident occurred at about 3:45am when seven carriages, comprising five second-class air-conditioned sleeping cars, one first-class sleeping car and one air-conditioned dining car, went off the tracks.

He said he believed it might have been due to the deteriorated condition of a bend in the tracks, where trains are usually required to lower their speed.

As a result of the derailment, both Chiang Mai- and Bangkok-bound trains are terminating services at Sila-at railway station in Uttaradit province, where passengers are being transferred to their destinations by bus.

Wongjan said one passenger was seriously injured. The rest suffered minor injuries and were provided free transport to their destinations.

Another Bangkok-bound train from Chiang Mai derailed early this month but no one was injured.